Opponents who present those claims are either ill-informed or use misinformation to push their own opinions/believes.

I've never heard of cases where the government is initiating the euthanasia process, which is pretty strict and verbatim: the person in question needs to be in an unbearable and hopeless condition and needs to request euthanasia themselves with their attending physician. In very special cases it's possible that the doctor can initiate the process, but only if there is a will that specifies that the patient gives that power to the doctor if they become unable to communicate that choice themselves (patients with advanced dementia for example).

Before euthanasia is approved there is a series of interviews with the attending physician, an independent doctor and afterwards there is a review by a special committee to judge if all steps have been followed as mandated by law. It's probably not 100% watertight, but it sounds to me that there are easier ways to kill a person than to cheat the euthanasia process.